New information on primate blood groups continued to accumulate during the eleventh grant year, though much hampered by the diminished number of animals available for study. This is due to the reduction in funding of this grant in the face of inflation and to the loss of other support for the animal colony now at the Laboratory for Experimental Medicine and Surgery in Primates (LEMSIP). Despite these handicaps, however, new blood factors were discovered during the past year as follows: Chimpanzee - Dc, Xc,Yc, Nc. Gibbons - three new, as yet unnamed factors. Baboons - GP, Np and four as yet unnamed factors. Geladas - one factor. Cynomologus macaques - Rhesus blood groups reagents found usable to blood group this species. Moreover, research productivity lost because of the loss of testing possibilities due to reduction in the number of animals was partly compensated for by theoretical work on consolidation of the available information, especially in chimpanzees. Overall, our studies have been aimed in a five-pronged direction: 1) Better understanding of human blood groups and the prevention of transfusion accidents. 2) Providing a model for experimental surgery in primates requiring blood transfusion. 3) Providing a model for experimental transplantation. 4) New immunological concepts. and 5) Zoology and anthropology.